1. Field of the Invention
This invention relates generally to a vehicle communications system that provides real-time traffic information and, more particularly, to a wireless vehicle-to-vehicle communications system where vehicles equipped with the system broadcast information about surrounding traffic that is then received and used and/or re-transmitted by other vehicles.
2. Discussion of the Related Art
Driver convenience systems, such as turn-by-turn navigation systems and digital map based navigation systems have been in development and use for some time, and have received favorable reviews for the benefits they provide to drivers. Some vehicle manufacturers have incorporated these types of systems in their vehicles or intend to have them in production in the near future.
Traffic accidents and roadway congestion are significant problems for vehicle travel. Providing continuous traffic information to a vehicle driver is available in today's vehicles through, for example, XM radio. One of the challenges in current traffic information systems is that the information is not in real-time, which means that there may be a considerable delay between collecting the traffic information and presenting it to a particular vehicle driver where sometimes the information may be outdated or misleading.
Vehicular ad-hoc network based active safety and driver assistance systems allow a wireless vehicle communications system to transmit messages to other vehicles in a particular area with warning messages about driving conditions. In these systems, multi-hop geocast routing protocols, known to those skilled in the art, are commonly used to extend the reachability of the warning messages, i.e., to deliver active messages to vehicles that may be a few kilometers away, as a one-time multi-hop transmission process. In other words, an initial message advising drivers of a certain situation is transferred from vehicle to vehicle using the geocast routing protocol so that relevant vehicles a significant distance away will receive the messages where one vehicle's direct transmission distance (range) is typically relatively short.
Vehicle-to-vehicle and vehicle-to-infrastructure applications require a minimum of one entity to send information to another entity. For example, many vehicle-to-vehicle safety applications can be executed on one vehicle by simply receiving broadcast messages from a neighboring vehicle. These messages are not directed to any specific vehicle, but are meant to be shared with a vehicle population to support the safety application. In these types of applications where collision avoidance is desirable, as two or more vehicles talk to each other and a collision becomes probable, the vehicle systems can warn the vehicle drivers, or possibly take evasive action for the driver, such as applying the brakes. Likewise, traffic control units can observe the broadcast of information and generate statistics on traffic flow through a given intersection or roadway.